This invention relates to improvements in pinch mechanisms. The invention is particularly suited for elastic rebound pinch mechanisms but is not limited thereto.
Problems exist when moving liquid with conventional pumping methods in which moving parts are exposed to product flow. For example:                Gears, seals, pistons and springs in contact with the product flow can very quickly succumb to corrosion, become blocked and or generally become in operative or faulty in operation        When used in an hygienic environment, or where one pump is used for a variety of liquids, these parts can be difficult to clean without disassembly        In some cases, peristaltic pumps have been used to try and address these issues, but poor tube life is often cited as a significant limiting factor.        
Elastic rebound pinch mechanisms are known. The mechanisms can function as a valve or as a pump. Generally the mechanism relies on a flexible tube or conduit having elastic rebound characteristics such that the tube can be pinched to close a flow passage through the tube and then released to enable the elastic rebound to restore the tube to substantially its non-deformed state. An elastic rebound pinch mechanism pump of the type disclosed in WO 99/01687 can overcome many of the above identified problems.
A problem which can arise with pinch mechanisms is that the rebound characteristics of the tube and/or the material from which it is constructed may not be sufficient to restore the tube to its fully non deformed state. Also the speed of movement of the tube to the non-deformed state can be slow. In a pumping situation failure to rebound fully or quickly can impair or at least limit the desired pump characteristics.
Furthermore the nature of the fluid material to be pumped or moved through the tube may require the tube to be made of a material (or of such thickness) that the elastic rebound characteristics do not permit the tube to rebound to its non-deformed state as fully or as quickly as desired. Alternately the material to flow through the tube may be of a viscosity or be sticky in nature such that once again the desired elastic rebound characteristics of the tube are impaired.